Method for forming and renewing wells



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E B. MOLL ETAL. METHOD FOR FORMING AND RENEWING WELLS Oct. 30, 1956 Filed March 26. 1952 NNN/@f INVENTORS BERNHARD MULL,y 0770 KR/EGBAUM- @www dz-, Ar TORNEYS METHOD FOR FORMING AND RENEWING WELLS Bernhard Moll, Wesseling, and Otto Kregbaum, Furth, Germany, assignors of one-half to Union Rheinische Braunkohlen Kraftstoff Aktiengesellschaft, Wesseling, Germany, a corporation of Germany, and one-half to Otto Kriegbanm, Furth, Germany Application March 26, 1952, Serial No. 27 8,617 4 Claims. (Cl. 16d-43) The present invention relates to a method of and a device for forming, maintaining and renewing wells; more particularly the invention concerns the treatment of strata and filter beds surrounding a well bore for the purpose of facilitating flow of fluid.

After making a well and delivering filter gravel into the borehole the well has to be cleaned from sand and nited States Patent O mud which is achieved by pumping. Adequate formation of the strata adjacent the filter bed so as to secure operation of the well without interference by sand for a number of years is attained only by pumping. For this purpose there has been used up to the present the well-known air-lift pump which apart from delivering water or oil, gives rise to an adequate formation about the well bore on account of its pulsating manner of action.

The production rate of wells which have been operated for prolonged periods, especially those frequently worked at the upper limit of their capacity, is gradually decreased even if the flowing conditions of the ambient oil or Water bearing strata have not changed. Such decline or production is believed to be due to the clogging of the filter medium or to an increase in density of the strata in the vicinity of the filter bed which may have various reasons. The afore-described drawbacks can only partly be overcome by the use of an air-lift pump.

it is an object of the present invention to provide a method of forming wells of high capacities. Another object of the invention is to start, maintain and increase the flow of wells by loosening accumulation in the filter pack and the producing strata. Further objects will become apparent as the following description proceeds.

In accordance with the present invention an especially suitable earth formation is achieved by intermittently causing the fluid in the strata surrounding a well bore to flow back, i. e. in countercurrent to the normal direction of flow. Such intermittent backffow of fluid is effected by producing in the borehole of a well an excess pressure by means of suitable pressure media. The normal inflow of fluid into the borehole is prevented by the excess pressure which forces the fluid to flow fback, i. e. away from the well bore. In consequence of the intermittent backflow of fluid the producing strata about the well bore are loosened and the loosened sand and mud particles are substantially removed in the following pumping operation. It has proved to be of particular advantage to employ a pressure gas, for instance air, which by conducting itf to the bottom of a well, forms, for instance with the water of the pump sump, a mixture of gas and water under pressure which migrates into and blows through the adjacent strata.

The present invention may be carried into effect by locating in the well casing an air-lift pump and a scavenging duct which is perforated at its lower part, and introducing gaseous material, for instance air, under pressure, into the scavenging duct. When the air-lift pump is at rest and the well casing hermetically sealed, the mixture of gas and water formed in the sump of the well is forced to migrate into the surrounding strata Patented Oct. 30, 1956 through the well tubing which is perforated at that part adjacent the oil or water bearing strata. The compressed air expands laterally away from the Well bore and draws the major part of the small-sized particles, mud and fine sand, from the gravel pack. By releasing the pressure in the scavenging duct and rendering the air-lift pump operative the backflow of fluid in the strata about the gravel pack is stopped and the normal inflow of fluid into the borehole is recovered. Any residual mud and sand particles are carried along by the normal flow of fluid and deposited at the bottom of the well bore from where they are delivered to the surface of the earth by inducing upward flow in the pump. By periodically repeat* ing the afore-described procedure, the filter pack and the water bearing strata about the gravel are continually and thoroughly loosened and cleaned, permeability of the filter bed and the strata being thus improved.

In the accompanying diagrammatic drawing which illustrates one embodiment of the invention by way of example, the figure is a sectional View of a well bore in which the filtering tube 1 is extended into the water bearing strata and is closed at the bottom 4. That portion of the casing adjacent the water bearing strata is perforated. The well shaft may also be lined with bricks. Pipe 2 which is open at the bottom, extended into the well bore and connected to the air intake 2a, is the stand pipe of an air-lift pump. The pipe 2 may also be used as the suction pipe of any other desired type of pump. The scavenging duct 3 is further installed in the well bore. Exclusion of air is secured by air-tightly leading all the ducts through plate 5 which hermetically seals the filtering tube 1. Back-flow of fluid is started by closing the slide valves 7 and 7a and introducing under pressure-imo the yscavenging duct 3 thrTgtlide A valy'li l,The exc p'fessure thus produced in the well bore forces the air-water mixture formed at the bottom 4 of the filtering tube 1 to migrate into the filtenpackand the surroundinggsutrgatmwhichare thus loosened. By clos'fgmtlewsiide valve 8 and opening the slide valves '7 and 7a water is delivered to the surface vthrough the stand pipe 2 by the action of the air-lift pump; water is again allowed to flow into the well bore. Together with the inflow of water fine, residual materials are drawn from the strata which have been loosened by the previous blowing action of the mixture of water and air. The alternate flow and backflow of fluid is continued until the water delivered to the surface no longer shows a marked turbidity or no longer contains noticeable amounts of sand or mud. Delivery of water may also be effected by means of an ordinary pump, however, the pulsating action of the air-lift pump has proved to be especially suitable for formation and recovery of circulation.

The increase in the production rate of a water well achieved according to the invention amounts to 20-30() percent depending upon the local conditions. The herein described method can also successfully be adapted to improve the production of seepage wells after the pore spaces and channels of the filter pack have become clogged with mud or oil. Furthermore, the invention`l` offers the possibility of withdrawing sand from wells even in such cases where the previously known methods failed to be successful.

The herein described method may not only successfully be adapted to start anew and to increase flow of failing wells or to maintain wells in flowing condition, but is particularly suited for forming new wells. Under certain conditions, for instance in the case of strata of sand or gravel, it is practicable according to the invention to withdraw smaller and smallest soil particles from each water bearing stratum areally and to allow or to facilitate the inflow of fluid into the well bore areally. Another advantage achieved according to the invention consists in that 3 the costs of building new wells are substantially reduced on account of the improved production rate which permits of making less deep-going well bores or boreholes of a smaller diameter.

Though the method and device of the invention have been described with specific reference to Water wells the invention is by no means intended to be restricted thereto but may also successfully be adapted to start, renew, maintain and increase the flow of oil wells, brine wells and mineral water wells. .cco-mrdingmtowa special embodiment of the invention the production of a well can still further be increased by addition of sui t a ble `ghern ical substances which are capable or dissowlyivngmolnoosening the strata and lter packs clogged `with sand, mud Ibrother materials. Chemical substances suitable for said purpose are, for instance, inorganicacidsmsuch as hydrochloric acid, sulfuric acid, nitric wacid, and hydrofluoric acid; furthermore, some organic acids forming water soluble salts, for instance oxalic acid and acetic acid. Solvents, especially organic solvents, for instance alcohols, hydrocarbons and chlorinated hydrocarbons, are likewise suitable to bring about the desired eiect. Further suitable chemical substances are oxidizing agents, for instance potassium permangeanate, hydrogen peroxide, oxygen and substances splitting off or yielding oxygen. The loosening elect of the oxidigzwipgiagent in the stratangglter packs is not only due to the dissolution of the materials clogging the strata and the gravel but perature aridY gessuredocciurring by introducing the said oxidiiigiagents. Furthermore, it is practicable to use mixtures of the substances suitable according to the invention. The aforesaid chemical substances may be added to the uid present at the sump of the well bore either before or during introduction of the pressure material.

We claim:

1. A method of increasing the flow of liquid in wells which comprises introducing a gaseous pressure medium into the lower portion of a sealed, perforated, wellcasing containing liquid therein, said gaseous medium being introduced in short, rapid pulses to produce a rapid, alternating ow of a mixture of gaseous pressure medium and liquid through the perforations of the well-casing niih-llglnding ih,....19 form a mixture of liquid and residiialniiiaterials and to return said mixture of liquid and residual materials from the earth strata into the well-casing, halting the introduction of said gaseous pressure medium into the Well-casing, thereafter withdrawing the mixture of liquid and residual materials from the well-casing, and periodically continuing the above cycle of operations until the liquid withdrawn from the well-casing is relatively free of residual materials.

2. The method of claim 1 wherein compressed air is employed as the gaseous pressure medium.

3. The method of claim 1 wherein acids are added, to the liquid in the well-casing ber-emitiiows into'thhe` earth strata.

4. The method of claim 1 wherein oxidizing agentsw are added to the liquid in the well-casing before it flows ,f into the earth strata.

5. The method of claim 1 wherein organic solvents are added to the liquid in the well-casing before it ows into the earth strata.

References Cited in the file of this patent UNITED STATES PATENTS 461,445 Monjeau Oct. 20, 1891 468,365 Robbins Feb. 9, 1892 657,951 Mooney Sept. 18, 1900 1,152,392 Breitung et al. Sept. 7, 1915 1,379,815 Hall May 31, 1921 1,448,997 Foggan Mar. 20, 1923 1,599,744 Chapmon Sept. 14, 1926 1,608,869 Tilton Nov. 30, 1926 1,809,546 Bowman June 9, 1931 

